Absorption of Dy3+ and Nd3+ ions in BaR 2F8 single crystals

The Dy³⁺ absorption and excitation spectra of BaY₂F₈ and BaYb₂F₈ single crystals are investigated in the ultraviolet, vacuum ultraviolet, and visible ranges at a temperature of 300 K. These crystals exhibit intense broad absorption bands due to the spin-allowed 4f-5d transitions in the range (56–78) × 10^?3 cm^?1 and less intense absorption bands that correspond to the spin-forbidden transitions in the range (50–56) × 10^?3 cm^?1. The Nd³⁺ absorption spectra of BaY₂F₈ single crystals are studied in the range (34–82) × 10^?3 cm^?1 at 300 K for different crystal orientations.     

Luminescence of yttrium aluminum borate single crystals doped with manganese

The optical absorption and luminescence spectra of single crystals of yttrium aluminum borate YAl₃(BO₃)₄ doped with manganese ions are measured. It is established that the optical absorption spectra of yttrium aluminum borate single crystals doped with manganese ions are determined primarily by the contribution from the Mn⁴⁺ ions. The luminescence spectra of the YAl₃(BO₃)₄ single crystals doped with manganese exhibit narrow lines attributed to the Mn⁴⁺ ions and an extended multiband structure which is associated primarily with the contribution from the Mn²⁺ ions.     

Broadening of the lines due to the 4f n -4f n − 15d transitions of Ce3+, Pr3+, and Tb3+ ions in the absorption spectra of CdF2 crystals

The structure of the absorption spectra of Ce³⁺, Pr³⁺, and Tb³⁺ ions in the vicinity of 4f-5d transitions has been investigated. At low temperatures the absorption spectra exhibit a weakly pronounced fine structure, in contrast to narrow-line spectra in crystals of Ca, Sr, and Ba fluorides. The spectra of Ce³⁺, Pr³⁺, and Tb³⁺ ions in CdF₂ can be considered as the absorption spectra of these ions in alkali-earth fluorides, broadened by 60–75 cm^?1. The broadening is related to the autoionization of electron from the local 5d(e _g ) level to the energy-degenerate states of the conduction band of CdF₂ crystal.     

Synthesis and spectroscopy of sodium-gadolinium tungstate NaGd(WO4)2 crystals activated by Tm3+ ions

Single crystals of disordered double sodium-gadolinium tungstate NaGd(WO₄)₂ doped with Tm ions were grown by the Czochralski method. The polarized absorption and emission spectra of these crystals with different activator concentrations and the decay kinetics of the ³ H ₄ and ³ F ₄ excited states of Tm³⁺ ions at 300 K were investigated. The absorption and emission cross sections of the expected laser transition ³ F ₄ ? ³ H ₆ in the Tm³⁺ ion were determined and the amplification spectra of the active laser medium NaGd(WO₄)₂:Tm at different levels of inverse population of the upper laser level ³ F ₄ of the Tm³⁺ ion were constructed. The prospects for using these crystals as active media in 2-μm solid-state lasers are discussed.     

UV and VUV spectroscopic study of Na0.4Y0.6F2.2 crystals doped with rare-earth ions

The short-wavelength transmission spectra of Na_0.4 R _0.6F_2.2 crystals with R = Y, Yb, or Lu have been investigated. For these crystals, the VUV transmission cutoffs are 78750, 58820, and 75200 cm^?1, respectively. The 4f ⁿ–4f ^n?15d absorption and excitation spectra of Na_0.4Y_0.6F_2.2 crystals activated with Ce³⁺, Pr³⁺, Nd³⁺, Er³⁺, Tm³⁺, and Yb³⁺ ions have been analyzed in the range 30000–80000 cm^?1. The energy positions of the lowest levels of the 4f ^n?15d configurations of these ions in the fluorite crystal matrix Na_0.4Y_0.6F_2.2 are determined. The absorption band in the spectral range 60600–70000 cm^?1 in Na_0.4(Y, Yb)_0.6F_2.2 crystals is due to the charge transfer from F^? to Yb³⁺. It is shown that the environmental symmetry of Ce³⁺ ions in Na_0.4R_0.6F_2.2 (R = Y, Yb, Lu) crystals is almost identical.     

Spectroscopic study of erbium-activated crystals of double calcium yttrium fluoride Ca<Subscript>0.89</Subscript>Y<Subscript>0.11</Subscript>F<Subscript>2.11</Subscript>:Er<Superscript>3+</Superscript>: I. Intensity of spectra and luminescence kinetics

Ca_0.89Y_0.11F_2.11:Er³⁺ (CYF:Er) crystals with an erbium content of 1–15 at % have been grown. The optical spectra and luminescence kinetics of CYF:Er crystals have been investigated at low (～5 K) and room temperatures. Based on an analysis of the absorption spectra at low temperature, the structure of Stark splitting of erbium levels in CYF:Er crystals is determined. Room-temperature absorption spectra are used to calculate the spectra of absorption cross sections and oscillator strengths of transitions from the erbium ground state to excited multiplets. It is shown that the absorption spectrum of CYF:Er crystals contains broad bands in the ranges of 790–815 and 965–980 nm, which correspond to the range of emission of laser diodes. For the band peaking near 967 nm, the peak absorption cross section is σ _abs ^max = 2.7 × 10^?21 cm². The intensity parameters are determined by the Judd-Ofelt method to be Ω₂ = 1.39 × 10^?20, Ω₄ = 1.34 × 10^?20, and Ω₆ = 2.24 × 10^?20 cm². The radiative transition probabilities, radiative lifetimes, and branching ratios are calculated with these values. The luminescence decay kinetics from excited erbium levels upon selective excitation is investigated and the experimental lifetimes of the 4F _9/2, ⁴ S _3/2, and ⁴ G _11/2 radiative erbium levels are determined. The dependences of multiphonon relaxation rates on the energy gap in CYF:Er crystals are obtained. The rates of nonradiative multiphonon relaxation from radiative erbium levels are determined.     

Photoluminescence, optical absorption and XRD studies on X-ray irradiated terbium doped KBr crystals

This paper reports the optical absorption, photoluminescence (PL), XRD, SEM studies made on KBr:Tb³⁺ crystals. The integrated light intensity is enhanced by about two orders of magnitude as compared to the undoped samples in spite of some OH^- present in the samples. PL of these crystals exhibits characteristic Tb³⁺ emissions due to transitions from the ⁵D₃ to ⁵D₄ levels to various levels of the ⁷F septet on F-bleaching X-ray irradiated crystals Z₃ centers are observed. The bands observed in the emission spectra of Tb³⁺ doped KBr are found to be shifted to higher wavelength. The stokes-shift of KBr:Tb³⁺ is determined and it is found to have a large value. The XRD studies have been made to determine the crystalline structure of KBr and KBr:Tb³⁺ and also the Miller indices. The SEM studies made reveal the presence of microcrystalline structure.     

Diffusionskonstante und charakteristische Absorption vor der Bandkante von Mn in ZnO-Kristallen

ZnO single crystals were doped with Mn and Co by diffusion. In the temperature range from 1400–1600 K the Mn and Co-diffusion-constants were determined:D _Mn=3.2 · 10^?3 exp (?2.87 eV/kT) cm² sec^?1 andD _Co=1·10exp(?3.98 eV/kT) cm² sec^?1. The Mn doped ZnO crystals show a characteristic colour due to an absorption near the intrinsic absorption edge. The corresponding absorption spectra were measured forE⊥c andE∥c. A discussion of different absorption mechanism shows that a charge-transfer transition is responsible for this absorption.     

The polarized reflection and absorption spectra of perylene crystals in monomeric and dimeric forms

The electronic absorption spectra of perylene crystals in the α- and β-forms were measured by the normal incidence reflection method in the spectral region from 20 000 to 60 000 cm^?1. From the absorption spectrum polarized perpendicular to [1$\text{1}$0] axis of the α-form crystal, the bands around 24 000 cm^?1 were determined to be polarized along the long molecular axis. Two strong bands with different polarizations were observed around 50 000 cm^?1 for each of the α- and β-perylene crystals and were assigned to the transitions to the ¹B_2u and ¹B_3u states. The observed polarized absorption spectra as a whole were consistent with the theoretical results by Hummel and Ruedenberg and the reflection method was found to be suitable to the polarized absorption measurement of strong bands of crystals. The observed factor-group splittings were compared with the theoretical values, the oriented gas model being found to be applicable to the β-form crystal.     

锂铌比对铪铁铌酸锂晶体全息存储性能的影响

以掺杂4 mol%Hf⁴⁺的LiNbO₃:Fe:Hf系列晶体（[Li]/[Nb]比变化）为研究对象,研究了系列晶体的可见吸收光谱,在632.8nm的写入光下晶体的衍射效率、灵敏度和抗光散射能力在不同[Li]/[Nb]下的变化规律.研究发现Hf⁴⁺的浓度达到阈值浓度后,随着[Li]/[Nb]比的增大,晶体的可见吸收边会发生红移,而且晶格中[Fe²⁺]/[Fe³⁺]也会增加,这就导致随着[Li]/[Nb]比的增加,样品的衍射效率逐渐减小,写入时间缩短,灵敏度增大.同时,在晶体中,随着[Li]/[Nb]的增大,陷阱中心Fe²⁺Li数量增大会使得晶体抗光散射能力减弱.     

Growth and spectroscopic studies of NaLa(MoO4)2:Tm3+ crystals: A new promising laser material

Single crystals of scheelite-like disordered double molybdate NaLa(MoO₄)₂ doped with thulium ions with dopant concentrations of 3.0 × 10¹⁹ and 1.2 × 10²⁰ cm^?3 are grown by the Czochralski method. Spectral and luminescent studies of crystals grown are performed in wavelength ranges of 800 nm (the transitions ³ H ₆?³ H ₄) and 2 μm (the transitions ³ H ₆?³ F ₄), including the measurements of the polarized absorption and luminescence spectra of these crystals and the decay kinetics of their excited states. A model that satisfactorily describes the decay kinetics of the luminescence from the ³ H ₄ level taking into account cross-relaxation interactions is proposed. The prospects for the use of these crystals as active media in two-micrometer solid-state lasers are discussed.     

Absorption and emission spectra of yttria-stabilized zirconia and magnesium oxide

We have investigated the luminescence and absorption spectra of doped and undoped ZrO₂-Y₂O₃ and MgO crystals at room- and low temperatures. The crystals used are partly doped with the transition metals Ni, Co, Cr and the rare earth Pr. The emission spectra were obtained under laser excitation at different wavelengths. The observed optical emission and absorption bands of the MgO crystals doped with Ni, Co and Cr correspond to transitions between spin-orbit split crystal field levels of the transition metals. Luminescence and absorption bands of undoped yttria-stabilized zirconia (YSZ) crystals are due to color centers, absorption bands of the doped YSZ correspond to the well known transitions of the Ni²⁺, Co²⁺ and Pr³⁺ ions, respectively. The emission spectra of the doped YSZ obtained under various laser excitations can be explained by an energy transfer process between the color center and the doping materials. The influence of annealing on the absorption and emission of Pr³⁺/Pr⁴⁺ is investigated.     

Growth and Study of Scintillation Properties of Orthovanadate Crystals Ca:GdVO<Subscript>4</Subscript> and Ca:YVO<Subscript>4</Subscript>

New scintillation orthovanadate crystals Ca:GdVO₄ and Ca:YVO₄ featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the ¹³⁷Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO₄ and Ca:GdVO₄ crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.     

Preparation and holographic storage properties of tri-doped Mg:Mn:Fe:LiNbO3 crystals

Doping MgO, MnO and Fe₂O₃ in LiNbO₃ crystals, tri-doped Mg:Mn:Fe:LiNbO₃ single crystals were prepared by the conventional Czochralski method. The UV-vis absorption spectra were measured and the shift mechanism of absorption edge was also investigated in this paper. In Mg:Mn:Fe:LiNbO₃ crystal, Mn and Fe locate at the deep level and the shallow level, respectively. The two-photon holographic storage is realized in Mg:Mn:Fe:LiNbO₃ crystals by using He-Ne laser as the light source and ultraviolet as the gating light. The results indicated that the recording time can be significantly reduced for introducing Mg²⁺ in the Mg:Mn:Fe:LiNbO₃ crystal.     

The electronic absorption spectra of [(CH3)3NH] MnCl3.2H2O single crystals

The electronic absorption spectra of [(CH₃)₃NH] MnCl₃.2H₂O single crystals are reported in the 15,000–45,000 cm^-1 region. In addition to the normally studied sextet → quartet transitions, special attention has been paid to the sextet → doublet transitions. Crystal field parameters evaluated (including the Trees' correction factor) to fit the observed spectra are B = 800, C = 2900, Dq = 680, and α = 76 cm^-1.     

中子探测晶体Li6Gd(BO3)3:Ce的光谱特性研究

文章用提拉法生长出Li₆Gd(BO₃)₃:Ce晶体,并对其光谱性能与发光过程进行了探索. 借助于真空紫外-紫外透过光谱测试,发现晶体的透过光谱中存在Ce³⁺离子和Gd³⁺的特征吸收峰,同时还存在与Ce⁴⁺离子相关的电荷迁移带. 对晶体的真空紫外-紫外激发发射光谱进行研究发现,在晶体存在着Ce³⁺离子的5d→4f辐射跃迁发光与Gd³⁺离子的4f→4f辐射跃迁发光,而且存在着Gd³⁺→Ce³⁺之间的能量传递. 对Li₆Gd(BO₃)₃:Ce晶体的X射线与γ射线激发发射光谱研究可知,晶体在高能射线激发下的闪烁光主要是Ce³⁺离子的发光. 关键词： 6Gd(BO₃)₃:Ce晶体')" href="#">Li₆Gd(BO₃)₃:Ce晶体 真空紫外-紫外透过光谱 真空紫外-紫外激发发射光谱 能量传递     

Growth and spectral properties of Nd:GdVO4 laser crystal

In this paper, the Czochralski growth, absorption spectra, and photoluminescence spectra of Nd:GdVO₄ crystals are studied. From its absorption spectra, Nd:GdVO₄ is found to exhibit an anisotropic optical absorption effect, and its effective Judd-Ofelt parameters are calculated: Ω₂=10.281×10⁻²⁰ cm², Ω₄=5.426×10⁻²⁰ cm² and Ω₆=9.943×10⁻²⁰ cm². By these parameters, the absorption oscillator strengths, emission oscillator strengths, transition probabilities, fluorescence branch ratios, energy lifetimes, and integrated emission cross-sections are also derived. The photoluminescence spectra of Nd:GdVO₄ crystal consist of a wide emission band of host and the characteristic emission bands of Nd³⁺. Based on the excitation spectrum, both the two evident peaks locating at 345 and 371 nm are ascribed to the characteristic excitation of Nd³⁺, and an energy transfer from the host to its doping Nd³⁺ ions is indicated.     

Growth and spectral characterization of β-Ga2O3 single crystals

Beta gallium oxide (β-Ga₂O₃) single crystals were grown by the floating zone technique. The absorption spectra and the luminescence of the crystals were measured. The absorption spectra showed an intrinsic short cutoff edge around 260 nm with two shoulders at 270 and 300 nm. Not only the characteristic UV (395 nm), blue (471 nm) and green (559 nm) lights, but also the red (692 nm) light can be seen in the emission spectra. The deep UV light was attributed to the existing of quantum wells above the valence band and the red light was owed to the electron-hole recombination via the vicinity donors and acceptors.     

Double exchange in cubic crystals with pairs of exchange-coupled mixed-valence 3<Emphasis Type="Italic">d</Emphasis><Superscript>3</Superscript>-3<Emphasis Type="Italic">d</Emphasis><Superscript>4</Superscript> ions

Specifics of the exchange interaction in mixed-valence Cr²⁺–Cr³⁺ 3d-ion pairs in KZnF₃ crystals are studied. It is shown that the double-exchange interaction can be significantly reduced by the low-symmetry crystal field created by a compensator. The features of the exchange interaction and optical absorption spectra are qualitatively analyzed.     

Charge conversion of uranium ions in CaF2

Single crystals of CaF₂ doped with uranium ions exhibiting a light red colour have been grown in an inert atmosphere. ESR spectra belonging to U³⁺ centers unstable at room temperature could be observed only after UV-irradiation at liquid nitrogen temperature. The formation and annealing of these centers as well as the optical absorption date indicate that a new charge conversion mechanism is effective in such crystals.